1. Field of the Invention
This invention relates to dispensers and more particularly to a chemical product selection and venturi eductor device for selectively dispensing and mixing, at a corresponding dilution ratio and total fluid flow rate, one of a plurality of fluids with another fluid.
2. Prior Art
Selector valves typically allow an operator to select and dispense one particular chemical fluid at a time, while closing off access to all of the other fluid sources available for selection. One such prior selector valve typically includes a static body having several inlet ports and one outlet port and a rotatable valve core with passages to allow selective connection of a selected inlet port with the outlet port. Sealing of the non-selected inlet ports is provided by a spring loaded, O-ring sealed plunger carried in the rotatable core and bearing against the face of the static body. While selector valves of this type allow for selective connection and dispensing of a plurality of fluids, they have several inherent disadvantages.
One problem associated with selector valves of this type is the ability to efficiently change over from one selected input chemical fluid to another. A residual volume of the prior chemical in many systems of this type must be purged prior to inputting a second selected chemical fluid. Purging the system is very detrimental in that it requires delays in the operation and diminishes the accuracy of the volume and timing of the mixing of the fluids. Because of the distance and the geometry of the path the selected fluid must travel within the selector valve system, the system may contain a significant amount of residual chemical after the user has selected a new inlet port, thereby requiring the user to spend time purging the line.
A contributing factor to the problem of residual fluids in the selector valve is turbulent flow of the fluids through the selector valve. Specifically, the cause of turbulent flow in the selected fluid flow path is commonly stagnation points or blind spots which are typically found at the juncture between mating components. These areas create turbulent flow of the fluid through the selector valve and minimize the ability to effectively purge the valve and flush the residual chemicals. Additionally, turbulent flow through the selector valve retards the fluid flow and requires greater pressures and timing problems for the selected input fluid sources and responsiveness of the selector valve and connected system components.
Two solutions to some of these identified problems are disclosed in U.S. Pat. Nos. 5,377,718 and 5,653,261 which are assigned to the assignee of the present invention. The systems of these patents reduce the amount of carry-over, or residual fluid, retained in the selector valve between dispensing selections by streamlining and reducing the volume of passages that retain residual fluid. Thus, in the illustrative embodiments contained therein, carry-over of less than 0.4 cc and less than 0.1 cc, respectively, are achieved.
While the systems disclosed in U.S. Pat. Nos. 5,377,718 and 5,653,261 solved a number of problems associated with prior selector valves, the systems were directed to reducing the amount of carry-over, and not to eliminating carry-over in the system. While many applications benefitted from the relatively small amount of carry-over, other applications were not suitable.
One specific prior art system avoiding chemical carryover is shown in FIG. 1. The dispensing system 10 uses two ball valves 12, 14, each directing a motive fluid, typically received from a pressurized water supply at a water inlet 16, to a respective eductor 18, 20. Thus, each selector valve 12, 14 does not direct or retain a chemical fluid. Instead, each chemical fluid is eductively drawn from a respective chemical fluid reservoir 22, 24 into the corresponding eductor 18, 20 downstream of the selector valve 12, 14, respectively, in response to the motive fluid. Mixed fluid from each eductor 18, 20 is dispensed from a common outlet 26. A third ball valve 28 supplies bypass water directly to the outlet 26 for purposes such as achieving a greater dilution, rinsing a hose (not shown) connected to the outlet 26, and rinsing articles (not shown).
While the dispensing system 10 efficiently mixes a number of chemical fluids for use from a single dispenser, further improvements are desired. For example, selecting a particular mixture requires positioning one or more of several different levers increases the opportunity for human error. In another example, use of several ball valves 12, 14, 28 increases the cost for selecting a chemical fluid, as compared to selector valves, such as disclosed in the above-referenced patents. In addition, a dispensing device be of a large size to position each ball valve and their levers.
Consequently, a significant need exists for a device for selectively mixing one or more of a chemical fluid with a motive fluid that is economic and smaller, yet does not carry-over chemical fluid between dispensing.
In accordance with principles of the present invention, in a preferred embodiment of the invention, a single selection member diverts a motive fluid to separate channels formed in an eductor body, at least one channel and preferably others being selectively and operatively associated with an eductor for drawing a chemical fluid. Thus, a single device is capable of selecting different mixed fluids without retaining a volume of residual fluid, or carry-over. A dispenser using the device can thus be smaller and more economically manufactured.
Consistent with one aspect of the invention, an apparatus for mixing at least one chemical fluid with a motive fluid has a selector body with a motive fluid passage and an eductor body with at least two fluid channels. Each fluid channel is in fluid communication between the motive fluid passage and a dispensing outlet. At least one fluid channel is an eductor whose venturi creates a low pressure when motive fluid passes through the eductor to draw a chemical fluid. Selecting the mixture of the motive fluid and the chemical fluid is achieved with a selector member that is contained within the motive fluid passage of the selector body to divert motive fluid to one or more of selected fluid channels. The single motive fluid selector member achieves an economy and efficiency over systems requiring a plurality of selector devices. In addition, since the selector member diverts motive fluid rather than a chemical fluid, carry-over of chemical fluids between dispensing selections is avoided.
In another aspect of the invention, a dispenser includes an apparatus with two eductors in the eductor body for mixing one of two chemical fluids, each supplied from a respective reservoir with a motive fluid; or alternatively for mixing the source chemical fluid from one or more sources but supplied at different flow rates. Also, different dilution rates may be produced by varying the flow rate of the motive fluid into the eductors. The selector member is positioned to divert motive fluid to at least one of the eductors to dispense the desired mixture.
Consistent with yet a further aspect of the invention, a method of mixing chemical fluids into a motive fluid without a carry-over of a previously selected chemical fluid includes the steps of (1) coupling a first supply of a chemical fluid to a venturi of a first eductor, (2) coupling a second supply of a chemical fluid to a venturi of a second eductor, (3) positioning a selector member to first position to divert the motive fluid to an inlet of the first eductor to dispense a first mixture, and (4) positioning the selector member to a second position to divert the motive fluid to an inlet of the second eductor to dispense a second mixture.
In short, prior art dispensing apparatus selected chemical sources by valves in the chemical lines. This invention contemplates a plurality of chemical eductors that are operated by a single valve in the motive fluid line diverting motive fluid to a selected eductor. Moreover, the motive fluid passage can be diverted to one or more chemical fluid channels connected to the same source to vary the dilution ratio of mixed fluid to be dispensed.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.